Abstract: A device for locking together two stacked objects, each having a plate with an opening, the plates being in superposed relation and the openings being in registry. The device includes a housing, the top wall of which is the plate of the lower object. A bolt, movable vertically and rotatably within the housing, having a head piece shaped to pass through the plate openings when the bolt is in a first angular orientation but not when the bolt is in a second angular orientation. A structural unit, movable vertically with the bolt and rotatable with respect to it, has a supporting shoulder which does not engage a support surface in the housing when the unit is in a first angular orientation but does engage the surface when the bolt is in a second angular orientation.